1. Field of the Invention
The present invention relates to a pattern processing system which corrects an outline of a pattern indicative of a character, a symbol etc. to perform reducing operation over the outline, and a method therefor.
2. Description of the Prior Art
As known, in desk top publishing (electronic publishing by personal computers), an outline font system is becoming a commonly adopted system in which a pattern of a character, a symbol, etc. is generated based on an outline font data. In the outline font system, the coordinates of a plurality of control points located on the outline of a pattern are held as data, and when it is desired to develop the pattern on a bit map, straight lines and/or curves passing through these control coordinate points are generated to form the outline and then fill dots in the inside area of the outline. According to this system, when enlarging or reducing a pattern, first the outline of the pattern is enlarged or reduced and then it is converted to a dot pattern. This is advantageous over a method for directly performing enlargement or reduction processing to the dot pattern in that this system causes less deterioration in the quality of the resultant character.
When an outline of a character is subjected to a reduction, it is not always preferable to reduce every portions of the outline proportionally. For example, when it is desired to reduce the outline of a pattern as shown in FIG. 10, two spacings t1 and t2 in the outline are originally different from each other. In the reduced outline, however, it is preferable to make the two spacings to be equal to each other because the pattern reduced in that manner, when developed on a bit map, can easily hold its quality. The pattern reduced in that manner can avoid such a situation as shown in FIG. 11 in which the slight difference between the spacings t1 and t2 is expressed in a difference of one picture element on the bit map. The reduced pattern in FIG. 11 is largely changed when compared with the original pattern. In conventional systems, however, the above-described correction processing to make equal the spacings in the reduced outline is not performed. Accordingly, the quality of a character may sometimes deteriorated when the character is reduced.
Laid-Open Publication No. 1-303489 of Japanese Patent Application proposes a character output system for solving a problem caused by a character pattern having unequal line widths. In this system, it is determined that each pair of opposing segments on the outline of a character pattern comprises a reference segment and a segment to be corrected and distance between the opposing segments in each pair is determined to be a reference width. When reducing the character pattern, the position of the reference segment is determined by reducing it and making it an integer value, while the position of the segment to be corrected is determined firstly by reducing its reference width and making it an integer value and then by positioning the segment to be corrected spaced from the position obtained based on the reference segment by the integer value obtained based on the reference width.
The character output system of the Laid-Open Publication can avoid a situation in which spacings between the opposing segments in each pair become unequal by the reduction processing of the pairs of segments. However, although the system can solve a problem that each pair of segments has unequal line width in a reduced character pattern, the system cannot perform such a correction for making uniform spacings between adjacent pairs of segments in an outline as shown in FIG. 10.